Slow vs fast doubling time and radiation effectiveness

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goodlife
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Date Joined May 2009
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   Posted 2/10/2011 4:10 PM (GMT -6)   
Does any have a good answer for why fast doubling time BCR seems to have a better chance of resulting in remission after radiation ? Does it imply that the recurrent PC is in the prostate bed and able to grow quickly as opposed to a systemic tumor that doesn't testosterone to eat ?

Goodlife

LV-TX
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Date Joined Jul 2008
Total Posts : 966
   Posted 2/10/2011 4:16 PM (GMT -6)   
Goodlife,

Little confused by the question. Systemic vs local are not apples to apples. If the cancer is local, then radiation or a combination of radiation and HT will normally do the trick. Systemic is not local and is outside the field of radation, except in those cases where the cancer is located in the pelvic lymph nodes and is also radiated.
You are beating back cancer, so hold your head up with dignity

Les

Robotic Surgery Sept 2008
PSA increasing since January 2009
Current PSA .44 (29 months)
PSA Doubling time approx. 6 months
Clinical Trial - SRT begins 2/21/11

goodlife
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Date Joined May 2009
Total Posts : 2691
   Posted 2/10/2011 4:24 PM (GMT -6)   
Les,
 
Sorry for the ambiguity.  I do understand that, but we really don't know after BCR if it is systemic or local.  Maybe that's what my question is leading to.
 
What I am referring to actually relates to a post by Purg that has a decison tree for radiation.  One of the studies says that if you have a fast doubling time, you are not a good candidate for radiation.   My question was does this mean it is most likely systemic if it is a slow doubling time ?
 
I find it a little confusing from a logic point of view.  I would assume that a slow doubling time was good, and therefore more easily treatable, but that's not what the study said.
 
Goodlife

Galileo
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Date Joined Nov 2008
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   Posted 2/10/2011 5:00 PM (GMT -6)   
It's more nuanced than a simple doubling time. There are multiple factors that are used in prediction , and even then it's only a predictor of odds for large groups of men.

In my case--bearing in mind that I am a person, not a study of thousands of men--my doubling time, post surgery, was rapid. It was doubling every 2.7 months. And yet I seem to have done fine, now nearly 4 years later, my PSA is still less than 0.1.

I would not sweat doubling time too much, but I would pay attention to the pre-SRT PSA level, since multiple studies have identified that as a crucial parameter.
Galileo

Dx Feb 2006, PSA 9 @age 43
RRP Apr 2006 - Gleason 3+4, T2c, NX MX, pos margins
PSA 5/06 <0.1, 8/06 0.2, 12/06 0.6, 1/07 0.7.
Salvage radiation (IMRT) Jan-Mar 2007
PSA 9/2007 and thereafter <0.1
pcabefore50.blogspot.com

Galileo
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Date Joined Nov 2008
Total Posts : 697
   Posted 2/10/2011 5:12 PM (GMT -6)   
Also, you may be thinking of the 2008 study by Trock that showed men with fast doubling time got the most survival benefit from SRT. My understanding is because men with slow doubling times weren't at high risk for dying from their recurrence, so SRT did not improve their survival (because it was already high). A subset of men with fast doubling times got the most bang for their SRT because their cancer was still localized.

Walsh was surprised about the findings:

"I found the results of this study remarkable," says Patrick C. Walsh, M.D., University Distinguished Service Professor of Urology at the Brady Urological Institute. "Previously, we believed that these men -who have aggressive disease defined by a rapid doubling of PSA in six months or less -- had distant metastases and would not benefit from any form of local salvage therapy."
(Personal comment: I was aware of these older recommendations when I went to meet my radiation oncologist the first time, and I was quite worried with my fast doubling time I'd go through SRT for nothing)

Some leading radiation oncologists (Dana-Farber, Harvard) commented:

"...we are also offering salvage radiotherapy to more patients with short doubling times and other unfavorable features, as the data suggest that there may be a group of patients with aggressive and rapidly progressing disease that remains localized to the prostate bed and that can be effectively salvaged by radiotherapy."

http://www.cancernetwork.com/prostate-cancer/content/article/10165/1617005
Galileo

Dx Feb 2006, PSA 9 @age 43
RRP Apr 2006 - Gleason 3+4, T2c, NX MX, pos margins
PSA 5/06 <0.1, 8/06 0.2, 12/06 0.6, 1/07 0.7.
Salvage radiation (IMRT) Jan-Mar 2007
PSA 9/2007 and thereafter <0.1
pcabefore50.blogspot.com

proscapt
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Date Joined Aug 2010
Total Posts : 644
   Posted 2/10/2011 5:18 PM (GMT -6)   
Goodlife - here is my limited understanding from reading some of the documents. It seems there are several different dynamics going on. It is not simple.

1.) If the cancer has a fast PSA doubling time, that is a sign of greater likelihood that it is no longer in the prostate bed and nearby lymph nodes but has become a metastatic, systemic disease. In that case local radiation will do no good whatsoever, since the cancer is no longer local. MRI and other imaging can often but not always reveal if this is the case. Also if you have a psa recurrence after having negative margins at RP it is more likely to be systemic but if you have a psa recurrence after having positive margins at RP it is more likely to be a local recurrence.

2.) If it is a fast doubling time, but it has not yet spread, that is all the more reason to hit it with radiation and hit it hard, before it spreads. PC with a fast doubling time is not always systemic.

3.) If it is localized and it is slow growing (PSADT > 15 months) there is an argument to be made for *not* doing RT even if the cancer appears to be localized, because most patients would die of something else before the PC ever got big enough to be symptomatic. This depends somewhat on age and co-morbidity of course.

Just because a cancer is no longer localized does not mean it is androgen-independent. It could go either way.

So you have to take multiple considerations into account. So perhaps think of it as a two by two matrix:
>> localized and slow growing - radiation can help but probably not needed, why suffer with the side effects?
>> localized and fast growing - nuke it
>> Systemic and slow growing - radiation can't help but you don't really need it.
>> Systemic and fast growing - radiation won't help at this point; seek to treat it by some other means.

The harder calls are when it is ambiguous whether localized or not, and when the growth rate is in the middle of the range between fast and slow.

Dr. Myers' video which purg posted recently has a lot of good thinking on this issue; I encourage you to review it.

Post Edited (proscapt) : 2/10/2011 6:21:08 PM (GMT-7)


Purgatory
Elite Member


Date Joined Oct 2008
Total Posts : 25380
   Posted 2/10/2011 5:26 PM (GMT -6)   
My understanding is the same logic as proscapt's points 1 through 3 above. This is how it was explained to me by the radiation doctor.
Age: 58, 56 dx, PSA: 7/07 5.8, 10/08 16.3
3rd Biopsy: 9/08 7 of 7 Positive, 40-90%, Gleason 4+3
open RP: 11/08, on catheters for 101 days
Path Rpt: Gleason 3+4, pT2c, 42g, 20% cancer, 1 pos marg
Incont & ED: None
Post Surgery PSA: 2/09 .05,5/09 .1, 6/09 .11. 8/09 .16
Post SRT PSA: 1/10 .12, 4/8 .04, 8/6 .06 11/10 Not taking it
Latest: 6 Corr Surgeries to Bladder Neck, SP Catheter since 10/1/9, SRT 39 Sess/72 gy ended 11/09, 21 Catheters, Ileal Conduit Surgery 9/23/10

goodlife
Veteran Member


Date Joined May 2009
Total Posts : 2691
   Posted 2/10/2011 7:04 PM (GMT -6)   
Thanks. I did watch Snuffy's video, and he made some kind of comment about fast doubling times should be treated with HT, between 3 and 6 month doubling times is a gray area, and longer doubling times are treated in a conservative manner. Not really consistent with the Trock report.
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